Emergency demolition of Christchurch hillside mansion

A former hillside mansion which once commanded one of the most priceless views in Christchurch has been demolished in an emergency operation today after fears it could topple down a cliff.

Canterbury Earthquake Recovery Authority (Cera) officials were working in the Redcliffs area on the Port Hills when a member of the public told them the earthquake-damage home had become unstable.

Some recent aftershocks, including a strong magnitude-4.2 jolt on Friday, is believed to have moved the five-storey house, built in the late 1990s, enough to put it on a lean and open up existing cracks.

Cera engineers were today so worried that it could collapse near the busy Main Rd below that workers flagged down a passing police patrol car and asked for help.

Officers helped close down the road while Cera tried to take some measures to stop the house, which also has a swimming pool, from falling.

Just one local resident was evacuated, while a couple more people returning to their properties were turned away.

"We told them to go to a coffee shop... they'll be back in tonight, " said Cera spokesman Brendan Winder, Port Hills land clearance project manager.

Crowds gathered below the house as a 30-tonne excavator began clawing at it from behind.

The plan was to bring it down on its own footprint within a few hours tonight, Mr Winder said.

Late last week, Cera discovered the building was "pretty distressed" and it was monitored over the weekend.

"We had another look at it again this morning... and the decision was made to knock the building over today," Mr Winder said.

He said they needed to "react quickly", given how it had deteriorated in recent days.

Given how many other hillside homes there are on the Port Hills, Cera knows "this may not be the last".

"Hopefully it is, but we need to be aware that there could be others out there as well," said Mr Winder.

"We'll go back and review our systems around how we're going to make sure we know more about these properties, but I don't have any particular concerns about any properties just now."